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 Bone and Soft-Tissue Disorders

= osteomalacia during enchondral bone growth

Age: 4–18 months

Histo: zone of maturation has an increase in the number of maturing cartilage cells with loss of normal columnar arrangement; zone of preparatory calcification does not form; failure of osteoid mineralization also in shafts so that osteoid production elevates periosteum

Location: metaphyses of long bones subjected to stress are particularly involved (wrists, ankles, knees); costochondral junction of ribs

mnemonic: “RICKETS”

  • Reaction of periosteum may occur
  • Indistinct cortex
  • Coarse trabeculation
  • Knees + wrists + ankles mainly affected
  • Epiphyseal plates widened + irregular
  • Tremendous metaphysis (fraying, splaying, cupping)
  • Spur (metaphyseal)

Cx: stress fracture, bowing deformity

Causes of Rickets  !!navigator!!

  1. ABNORMALITY IN VITAMIN D METABOLISM associated with reactive hyperparathyroidism
    1. Vitamin D deficiency (most common cause)
      1. dietary lack of vitamin D = famine osteomalacia = nutritional lack of vitamin precursors (vegetarian diet, prolonged total breast feeding without vitamin D supplementation)
      2. lack of sunshine exposure eg, residence in high latitudes, clothing covering skin, sunshine avoidance for religious / cultural reasons, heavy skin pigmentation
      3. malabsorption of vitamin D
        = gastroenterogenous rickets due to
        1. Pancreatitis + biliary tract disease
        2. Steatorrhea, celiac disease, postgastrectomy
        3. Inflammatory bowel disease
    2. Defective conversion of vitamin D to 25-OH-cholecalciferol (vitamin D3) in liver
      1. Liver disease
      2. Anticonvulsant drug therapy (= induction of hepatic enzymes that accelerate degradation of biologically active vitamin D metabolites)
    3. Defective conversion of prehormone calcifediol [25(OH)D3] to cholecalciferol [1,25(OH)2D3] in kidney
      1. Chronic renal failure = renal osteodystrophy
      2. Vitamin D–dependent rickets = autosomal recessive enzyme defect of 25(OH)D-1α-hydroxylase
  2. II. ABNORMALITY IN PHOSPHATE METABOLISM not associated with hyperparathyroidism ← normal serum calcium
    1. Phosphate deficiency
      1. Intestinal malabsorption of phosphates
      2. Ingestion of aluminum salts [Al(OH)3] forming insoluble complexes with phosphate
      3. Low phosphate feeding in prematurely born infants
      4. Severe malabsorption state
      5. Parenteral hyperalimentation
    2. Disorders of renal tubular reabsorption of phosphate
      1. Renal tubular acidosis (renal loss of alkali)
      2. deToni-Debré-Fanconi syndrome = hypophosphatemia, glucosuria, aminoaciduria
      3. Vitamin D–resistant rickets
      4. Cystinosis
      5. Tyrosinosis
      6. Lowe syndrome
      7. Ifosfamide nephrotoxicity (for the treatment of rhabdomyosarcoma, Wilms tumor)
    3. Hypophosphatemia with nonendocrine tumors
      = Oncogenic rickets = elaboration of humeral substance which inhibits tubular reabsorption of phosphates (paraneoplastic phenomenon)
      1. Nonossifying fibroma
      2. Sclerosing hemangioma
      3. Hemangiopericytoma
      4. Ossifying mesenchymal tumor
    4. Hypophosphatasia
  3. III. CALCIUM DEFICIENCY
    1. Dietary rickets = milk-free diet (extremely rare)
    2. Malabsorption
    3. Consumption of substances forming chelates with calcium

Classification of Rickets  !!navigator!!

  1. Primary vitamin D–deficiency rickets
  2. II. Gastrointestinal malabsorption
    1. Partial gastrectomy
    2. Small intestinal disease: gluten-sensitive enteropathy / regional enteritis
    3. Hepatobiliary disease: biliary atresia / chronic biliary obstruction / biliary cirrhosis resulting in failure of the emulsifying action of bile salts (fat-soluble vitamin) or failure of conversion
    4. Pancreatic disease: chronic pancreatitis
  3. III. Primary hypophosphatemia; vitamin D–deficiency rickets
  4. IV. Renal disease
    1. Chronic renal failure
    2. Renal tubular disorders: renal tubular acidosis
    3. Multiple renal defects
  5. Hypophosphatasia + pseudohypophosphatasia
  6. VI. Fibrogenesis imperfecta osseum
  7. VII. Axial osteomalacia
  8. VIII. Miscellaneous:
    Hypoparathyroidism, hyperparathyroidism, thyrotoxicosis, osteoporosis, Paget disease, fluoride ingestion, ureterosigmoidostomy, neurofibromatosis, osteopetrosis, macroglobulinemia, malignancy

 Outline